Image sensor and display device having the same

ABSTRACT

An image sensor includes a sensor pixel. The sensor pixel includes a first transistor coupled between a first power source and a first node, where the first transistor is turned on in response to a first control signal, a light-sensing element coupled between the first node and a second power source, where the light-sensing element generates photocharges in response to incident light, a storage capacitor coupled in parallel to the light-sensing element between the first node and the second power source, and an amplifier including a plurality of transistors coupled in series between the first power source and an output line, where the amplifier outputs a sensing signal corresponding to a voltage of the first node in response to a first driving signal.

This application is a continuation of U.S. patent application Ser. No.17/750,687, filed on May 23, 2022, which is a divisional of U.S. patentapplication Ser. No. 16/799,049, filed on Feb. 24, 2020, which claimspriority to Korean patent application number 10-2019-0038706, filed onApr. 2, 2019, and all the benefits accruing therefrom under 35 U.S.C. §119, the content of which in its entirety is herein incorporated byreference.

BACKGROUND 1. Field

Embodiments of the disclosure relate to an image sensor and a displaydevice including the image sensor.

2. Description of the Related Art

Recently, display devices provided in various mobile devices including asmartphone and a tablet personal computer (“PC”) have been utilized invarious aspects. For example, display devices have been manufactured tosupport various functions, such as a function of recognizing a user'sfingerprint or a surrounding environment or a scanner function.Accordingly, display devices, each including an image sensor, have beenwidely used.

SUMMARY

Embodiments of the disclosure are directed to an image sensor withreduced noise and a display device including the image sensor.

An embodiment of the disclosure provides an image sensor including asensor pixel. The sensor pixel includes: a first transistor coupledbetween a first power source and a first node, where the firsttransistor is turned on in response to a first control signal; alight-sensing element coupled between the first node and a second powersource, where the light-sensing element generates photocharges inresponse to incident light; a storage capacitor coupled in parallel tothe light-sensing element between the first node and the second powersource; and an amplifier including a plurality of transistors coupled inseries between the first power source and an output line, where theamplifier outputs a sensing signal corresponding to a voltage of thefirst node in response to a first driving signal.

In an embodiment, the amplifier may include a second transistor coupledbetween the first power source and the output line, where the secondtransistor includes a gate electrode coupled to the first node andgenerates the sensing signal; and a third transistor coupled between thesecond transistor and the output line, where the third transistoramplifies and outputs the sensing signal during an interval in which thefirst driving signal is supplied.

In an embodiment, the amplifier may further include a fourth transistorcoupled between the third transistor and the output line. The fourthtransistor may amplify and output a sensing signal supplied from thethird transistor during the interval in which the first driving signalis supplied.

In an embodiment, the image sensor may further include a first drivingline coupled in common to gate electrodes of the third and fourthtransistors, where the first driving line transmits the first drivingsignal therethrough; and a first resistor element coupled between thegate electrode of the third transistor and the first driving line.

In an embodiment, the first resistor element may include a transistorelement coupled in a form of a diode between the first driving line andthe gate electrode of the third transistor.

In an embodiment, the amplifier may include a second resistor elementcoupled between the first resistor element and the first driving line;and a fifth transistor coupled between the third transistor and thefourth transistor, where the fifth transistor includes a gate electrodecoupled between the first and second resistor elements.

In an embodiment, the image sensor may further include a first drivingline coupled to the gate electrode of the fourth transistor, where thefirst driving line transmits the first driving signal therethrough; anda second driving line coupled to the gate electrode of the thirdtransistor, where the second driving line transmits a second drivingsignal therethrough during the interval in which the first drivingsignal is supplied.

In an embodiment, the second driving signal may have a gate-on voltagelower than a voltage level of the first driving signal.

In an embodiment, the image sensor may further include a fifthtransistor coupled between the third transistor and the fourthtransistor, and a third driving line coupled to a gate electrode of thefifth transistor, where the third driving line transmits a third drivingsignal, which overlaps the first and second driving signals,therethrough.

In an embodiment, the third driving signal may have a gate-on voltagewhich is higher than a voltage level of the second driving signal and islower than a voltage level of the first driving signal.

In an embodiment, wherein, during each cycle of a sensing period inwhich the sensor pixel is activated, the first control signal and thefirst driving signal may be sequentially supplied to the sensor pixel atan interval of a predetermined time.

In an embodiment, the light-sensing element may be a photodiode.

In an embodiment, the sensor pixel may further include a transfertransistor coupled between the first node and the light-sensing element,where the transfer transistor is turned on in response to a secondcontrol signal.

In an embodiment, the first and second control signals may besequentially supplied to the sensor pixel during each cycle of a sensingperiod during which the sensor pixel is activated, and the first drivingsignal may be individually supplied subsequent to the first and secondcontrol signals a plurality of times during each cycle.

Another embodiment of the disclosure provides for a display device. Thedisplay device includes a display panel including a display pixel; andan image sensor including a sensor pixel. The sensor pixel includes: afirst transistor coupled between a first power source and a first node,where the first transistor is turned on in response to a first controlsignal; a light-sensing element coupled between the first node and asecond power source, where the light-sensing element generatesphotocharges in response to incident light; a storage capacitor coupledin parallel to the light-sensing element between the first node and thesecond power source; and an amplifier including a plurality oftransistors coupled in series between the first power source and anoutput line, where the amplifier outputs a sensing signal correspondingto a voltage of the first node in response to a first driving signal.

In an embodiment, the amplifier may include a second transistor coupledbetween the first power source and the output line, where the secondtransistor includes a gate electrode coupled to the first node togenerate the sensing signal; and a third transistor coupled between thesecond transistor and the output line, where the third transistoramplifies and outputs the sensing signal during an interval in which thefirst driving signal is supplied.

In an embodiment, the amplifier may further include a fourth transistorcoupled between the third transistor and the output line, and the fourthtransistor amplifies and outputs a sensing signal supplied from thethird transistor during the interval in which the first driving signalis supplied.

In an embodiment, during each cycle of a sensing period in which thesensor pixel is activated, the first control signal and the firstdriving signal are sequentially supplied to the sensor pixel at aninterval of a predetermined time.

In an embodiment, the sensor pixel may further include a transfertransistor coupled between the first node and the light-sensing element,where the transfer transistor is turned on in response to a secondcontrol signal.

In an embodiment, the image sensor may be arranged on a rear surface ofthe display panel, and the sensor pixel may be arranged in a sensingarea, which overlaps a portion of a display area in which the displaypixel is arranged.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the invention will become apparent bydescribing in detail exemplary embodiments thereof with reference to theaccompanying drawings, in which:

FIG. 1 is a configuration diagram illustrating a display deviceaccording to an embodiment of the disclosure;

FIGS. 2 and 3 are plan views illustrating the panel unit of a displaydevice according to an embodiment of the disclosure;

FIGS. 4A to 4D are plan views illustrating an array structure of displaypixels and sensor pixels according to an embodiment of the disclosure;

FIGS. 5A and 5B are sectional views illustrating a display deviceaccording to an embodiment of the disclosure;

FIG. 6 is a circuit diagram illustrating a display device according toan embodiment of the disclosure;

FIG. 7 is a sectional view illustrating a display pixel according to anembodiment of the disclosure;

FIG. 8 is a circuit diagram illustrating a sensor pixel according to anembodiment of the disclosure;

FIG. 9 is a signal timing diagram illustrating an embodiment of inputsignals for driving the sensor pixel of FIG. 8 ;

FIG. 10 is a circuit diagram illustrating a sensor pixel according to analternative embodiment of the disclosure;

FIG. 11 is a signal timing diagram illustrating another alternativeembodiment of input signals for driving the sensor pixel of FIG. 10 ;

FIG. 12 is a circuit diagram illustrating a sensor pixel according toanother alternative embodiment of the disclosure;

FIG. 13 is a circuit diagram illustrating a sensor pixel according to anembodiment of the disclosure;

FIG. 14 is a circuit diagram illustrating a sensor pixel according toanother alternative embodiment of the disclosure;

FIG. 15 is a signal timing diagram illustrating an embodiment of inputsignals for driving the sensor pixel of FIG. 14 ;

FIG. 16 is a circuit diagram illustrating a sensor pixel according toanother alternative embodiment of the disclosure;

FIG. 17 is a circuit diagram illustrating a sensor pixel according toanother embodiment of the disclosure; and

FIG. 18 is a signal timing diagram illustrating an embodiment of inputsignals for driving the sensor pixel of FIG. 17 .

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. Like reference numerals refer tolike elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “At least one of A and B” means “A or B.” “Or” means“and/or.” As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. It will befurther understood that the terms “comprises” and/or “comprising,” or“includes” and/or “including” when used in this specification, specifythe presence of stated features, regions, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, regions, integers, steps,operations, elements, components, and/or groups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother elements as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, embodiments of the invention will be described in detailwith reference to the accompanying drawings.

FIG. 1 is a configuration diagram illustrating a display device 10according to an embodiment of the disclosure. In accordance with anembodiment, a panel unit 100 and a driver unit 200 of the display device10 may be separate or independent components as shown in FIG. 1 , butnot being limited thereto. In an alternative embodiment, a part of adisplay driver 210 may be integrated with a display panel 110. In anembodiment, an image sensor 120 and a sensor driver 220 may collectivelydefine or constitute a single sensor (e.g., a fingerprint sensor or thelike).

Referring to FIG. 1 , an embodiment of the display device 10 may includethe panel unit 100 and the driver unit 200. In accordance with anembodiment, the panel unit 100 may include the display panel 110configured to display an image and the image sensor 120 arranged on asurface of the display panel 110. In such an embodiment, the driver unit200 may include the display driver 210 which drives the display panel110 and the sensor driver 220 which drives the image sensor 120.

The display panel 110 may include a plurality of display pixels todisplay an image corresponding to input image data. In an embodiment,the display panel 110 may be, but is not limited to, a light-emittingdisplay panel including organic/inorganic light-emitting elements or aliquid display panel including a liquid crystal layer. In embodiments ofthe invention, the type and/or structure of the display panel 110 is notparticularly limited and may be changed in various forms.

The image sensor 120 may include a plurality of sensor pixels forgenerating sensing signals corresponding to incident light. In anembodiment, the image sensor 120 may be arranged on a rear surface ofthe display panel 110. In such an embodiment, various functions, such asa function of recognizing a user's fingerprint or a surroundingenvironment or a scanner function, may be realized using the imagesensor 120 while the degradation of image quality caused by the imagesensor 120 is effectively prevented.

The display driver 210 may include driver circuits which supply varioustypes of driving signals to the display panel 110. In one embodiment,for example, the display driver 210 may include a scan driver and a datadriver which supply scan signals and data signals, respectively, todisplay pixels.

The sensor driver 220 may include various types of driving/sensingcircuits for driving the image sensor 120 and acquiring sensedinformation based on sensing signals output from the image sensor 120.In one embodiment, for example, the sensor driver 220 may include atransmission (“Tx”) circuit unit which supplies various types of drivingsignals and/or control signals to sensor pixels, and a reception (“Rx”)circuit unit which receives sensing signals output from the sensorpixels in response to the driving signals, analyzes the sensing signals,and generates sensed information. In an embodiment, the Tx circuit unitmay have a plurality of Tx channels corresponding to driving lines ofthe image sensor 120 (e.g., driving lines arranged in respectivehorizontal rows of the image sensor 120). In such an embodiment, the Rxcircuit unit may include a plurality of Rx channels corresponding tooutput lines of the image sensor 120 (e.g., output lines arranged inrespective vertical columns of the image sensor 120).

FIGS. 2 and 3 are plan views illustrating the panel unit 100 of thedisplay device 10 according to an embodiment of the disclosure.Particularly, FIGS. 2 and 3 illustrate embodiments of the display panel110 and the image sensor 120 having different array structures from eachother.

Referring to FIGS. 2 and 3 , an embodiment of the display panel 110 mayinclude display pixels PXLd arranged in a display area DA. The imagesensor 120 may include sensor pixels PXLi arranged in a sensing area SAand may be arranged to overlap at least a portion of the display panel110. In one embodiment, for example, the image sensor 120 may bearranged on a rear surface of the display panel 110 in a way such thatthe sensing area SA overlaps at least a portion of the display area DA.

In an embodiment, the image sensor 120 may be arranged to overlap aportion of the display panel 110, and the image sensor 120 may have asize (e.g., an area) smaller than that of the display panel 110, asillustrated in FIG. 2 . In an embodiment, the sensing area SA mayoverlap a portion of the display area DA.

In an alternative embodiment, the image sensor 120 may be arranged tooverlap the display panel 110, and the image sensor 120 may have a size(e.g., an area) substantially identical to or similar to that of thedisplay panel 110, as illustrated in FIG. 3 . In such an embodiment, thesensing area SA may be arranged to substantially entirely overlap thedisplay area DA.

However, the disclosure is not limited thereto. In such an embodiment,the sizes and/or array structure of the display panel 110 and the imagesensor 120 may be variously modified.

The display panel 110 may include the display area DA and a non-displayarea NDA. The display area DA may be defined on a screen of the displaydevice 10. The non-display area NDA may be arranged around the displayarea DA, and may be disposed, for example, in a peripheral region of thedisplay panel 110 to surround the display area DA.

The display area DA may be an area in which a plurality of displaypixels PXLd is arranged and may also be referred to as an active area ofthe display device 10. In an embodiment, the display pixels PXLd may bepixels having various types and/or structures. In one embodiment, forexample, the display pixels PXLd may be pixels of a light-emittingdisplay panel, each having an light-emitting element. The display device10 displays an image in the display area DA by driving the displaypixels PXLd based on input image data.

The non-display area NDA may be an area disposed around the display areaDA and may also be referred to as the non-active area of the displaydevice 10. Herein, the non-display area NDA may inclusively mean an areaof the display panel 110 other than the display area DA. In anembodiment, the non-display area NDA may include a wiring area, a padarea and/or various types of dummy areas.

The image sensor 120 may include the sensing area SA in which sensorpixels PXLi are arranged in a way such that the shape of a target (e.g.,a specific pattern or the like of the target), such as a user'sfingerprint, and/or the brightness of the target may be effectivelysensed. In accordance with an embodiment, the sensing area SA may be setto an area overlapping only a portion of the display area DA, asillustrated in FIG. 2 , or to an area overlapping the entire displayarea DA, as illustrated in FIG. 3 . Alternatively, the display area DAand the sensing area SA may be arranged in a way such that only partialregions thereof overlap each other. In an embodiment, each of the sensorpixels PXLi may include a light-sensing element (or also referred to asa “light-receiving element”) to generate a sensing signal correspondingto incident light.

In an embodiment, as a light source of the image sensor 120, a lightsource arranged in the display panel 110 may be used. In one embodiment,for example, a light-emitting element provided in a display pixel PXLdmay be used as a light source for fingerprint sensing or the like. Inone embodiment, for example, during a predetermined sensing period inwhich a fingerprint sensing mode or the like is activated, at least someof the display pixels PXLd overlapping the sensing area SA emit light,and the image sensor 120 may operate using internal light of the displaypanel 110 from the display pixels PXLd. In such an embodiment, thedisplay pixels PXLd are used as the light sources of the image sensor120 without using a separate external light source, such that thethickness of the display device 10 may be reduced or minimized, andmanufacturing costs may be decreased.

However, the disclosure is not limited thereto. In an alternativeembodiment, in addition to the light-emitting elements of the displaypixels PXLd used for image display, a separate light source may bedisposed inside/outside the display panel 110 and may be used as thelight source of the image sensor 120.

FIGS. 4A to 4D are plan views illustrating an array structure of displaypixels PXLd and sensor pixels PXLi according to an embodiment of thedisclosure. Particularly, FIGS. 4A to 4D illustrate relative sizes,resolution and/or array relations of display pixels PXLd and sensorpixels PXLi arranged in the sensing area SA of FIGS. 2 and 3 and thedisplay area DA overlapping the sensing area SA. However, the disclosureis not limited to the embodiments illustrated in FIGS. 4A to 4D, and theshapes, array forms, relative sizes, numbers, resolution, and/or mutualarray relations of the display pixels PXLd and/or the sensor pixels PXLimay be variously modified.

In the above description of the embodiments in FIGS. 2 and 3 , thesensing area SA and the display area DA have been described asindependent or separate elements to describe an area in which the sensorpixels PXLi are arranged in the image sensor 120 and an area in whichthe display pixels PXLd are arranged in the display panel 110. FIGS. 4Ato 4D illustrate an array structure of display pixels PXLd and sensorpixels PXLi in an area in which the sensing area SA and the display areaDA overlap each other, and a portion of the display device 10 in whichthe display pixels PXLd and the sensor pixels PXLi are arranged togetherwill be inclusively referred to as a “sensing area SA”.

In an embodiment, referring to FIG. 4A, sensor pixels PXLi may bearranged with a same resolution (or a same density) as display pixelsPXLd in the sensing area SA. In one embodiment, for example, in thesensing area SA, a number of sensor pixels PXLi arranged therein may beidentical to the number of display pixels PXLd arranged therein, and thesensor pixels PXLi may be arranged to form pairs with the display pixelsPXLd in a one-to-one correspondence.

In an embodiment, the display pixels PXLd and the sensor pixels PXLi mayoverlap each other while forming pairs in a one-to-one correspondence,as illustrated in FIG. 4A. In such an embodiment, at least a portion ofeach of the sensor pixels PXLi may overlap any one display pixel PXLd.In one embodiment, for example, each sensor pixel PXLi may be arrangedin a pixel area in which one display pixel PXLd is formed, and thesensor pixel PXLi may have a size smaller than that of the correspondingdisplay pixel PXLd. Here, the term “pixel area” may inclusively mean anarea in which at least one light-emitting element and/or a pixel circuitwhich constitute each display pixel PXLd are disposed.

However, in such an embodiment, the array structure of display pixelsPXLd and sensor pixels PXLi may be variously modified or changed invarious forms. In an alternative embodiment, the display pixels PXLd andthe sensor pixels PXLi are arranged adjacent to each other while formingrespective pairs in a one-to-one correspondence, but the display pixelsPXLd and the sensor pixels PXLi may be alternately arranged in a waysuch that the display pixels PXLd and the sensor pixels PXLi do notoverlap each other. Alternatively, the display pixels PXLd and thesensor pixels PXLi may be alternately arranged not to overlap each otherregardless of the relative sizes and/or the numbers of display pixelsPXLd and sensor pixels PXLi.

Referring to FIG. 4B, in an embodiment, sensor pixels PXLi may bearranged between display pixels PXLd not to overlap the display pixelsPXLd. In an embodiment, sensor pixels PXLi may arranged in the sensingarea SA to have resolution (or density) identical to or different fromthat of display pixels PXLd. In an embodiment, the sensor pixels PXLimay have a size identical to or different from that of the displaypixels PXLd. Alternatively, the sensor pixels PXLi may be arranged inthe sensing area SA to have a predetermined size and/or predeterminedresolution regardless of the size and/or the resolution of the displaypixels PXLd.

Referring to FIG. 4C, the sensing area SA may include sensor pixelsPXLi, the number of which is less than the number of the display pixelsPXLd. In such an embodiment, the sensor pixels PXLi may be distributedover the sensing area SA at resolution lower than that of the displaypixels PXLd. In one embodiment, for example, each sensor pixel PXLi maybe arranged in the sensing area SA to have such a size and/or atinterval determined in a way such that each sensor pixel PXLi is allowedto overlap a plurality of display pixels PXLd arranged in the sensingarea SA.

In such an embodiment, the sensor pixels PXLi may be distributed overthe sensing area SA at resolution lower than that of the display pixelsPXLd, and a distribution form thereof may be changed or variouslymodified. In an alternative embodiment, the sensor pixels PXLi may bearranged to overlap only some of the display pixels PXLd arranged in thesensing area SA. Alternately, in the sensor pixels PXLi may be arrangednot to overlap the display pixels PXLd while being distributed over thesensing area SA at resolution lower than that of the display pixelsPXLd.

Referring to FIG. 4D, the sensing area SA may include sensor pixelsPXLi, the number of which is greater than the number of the displaypixels PXLd. In such an embodiment, the sensor pixels PXLi may bedistributed over the sensing area SA at resolution higher than that ofthe display pixels PXLd. In one embodiment, for example, some of sensorpixels PXLi arranged in the sensing area SA may overlap display pixelsPXLd, and some other sensor pixels PXLi may be arranged between displaypixels PXLd.

In an embodiment, where sensor pixels PXLi may be distributed over thesensing area SA at resolution higher than that of display pixels PXLd,the sensor pixels PXLi may be arranged not to overlap the display pixelsPXLd. In one embodiment, for example, sensor pixels PXLi may be denselyarranged only in regions between display pixels PXLd while having a sizesmaller than that of the display pixels PXLd.

In an embodiment, as shown in FIG. 4D, sensor pixels PXLi may beregularly arranged in the sensing area SA, but the disclosure is notlimited thereto. In an alternative embodiment, sensor pixels PXLi may beirregularly distributed over the sensing area SA. In such an embodiment,the sizes, resolution and/or distribution forms of sensor pixels PXLimay be variously modified or changed in various manners.

FIGS. 5A and 5B are sectional views illustrating the display device 10according to an embodiment of the disclosure. Particularly, FIGS. 5A and5B schematically illustrate a fingerprint sensing method using thedisplay device 10 together with a schematic section of the sensing areaSA of the display device 10.

Referring to FIGS. 5A and 5B, an embodiment of the display device 10 mayinclude a display panel 110 including display pixels PXLd, and an imagesensor 120 and a window 130 respectively arranged on opposite surfacesof the display panel 110. In an embodiment, the image sensor 120 and thewindow 130 may be respectively arranged on a rear surface and a frontsurface of the display panel 110. In an embodiment, the window 130 maybe selectively provided in the display device 10. In an alternativeembodiment, the window 130 may be omitted or may be integrated with thedisplay panel 110.

In an embodiment, the display panel 110 and the image sensor 120 mayoverlap each other at least in a sensing area SA. In accordance with anembodiment, sensor pixels PXLi may be distributed over the sensing areaSA at a resolution higher than that of display pixels PXLd, asillustrated in FIG. 5A, or may be distributed over the sensing area SAat resolution lower than that of the display pixels PXLd, as illustratedin FIG. 5B. In an embodiment, the sensor pixels PXLi may be distributedover the sensing area SA, with at least a resolution sufficient toperform a sensing function. In one embodiment, for example, when theimage sensor 120 is designed to sense a fingerprint, the sensor pixelsPXLi may be distributed over the sensing area SA, with at least aresolution (or density) sufficient to identify a fingerprint.

In an embodiment, the display device 10 may sense a fingerprint or thelike using at least some of the display pixels PXLd as light sources. Inone embodiment, for example, during a sensing period in which the imagesensor 120 is activated, the display device 10 may generate internallight of the display panel 110 by driving at least some of the displaypixels PXLd distributed over the sensing area SA. In one embodiment, forexample, the display device 10 may emit light by driving at least someof display pixels PXLD in the sensing area SA and by causinglight-emitting elements EL in the driven display pixels to emit light.

In such an embodiment, when a user's finger touches or approaches thetop surface of the display device 10, for example, the window 130 of thesensing area SA, at least part of light emitted from the display panel110 may be reflected from the user's finger, and then may be incident onthe sensor pixels PXLi after sequentially passing through the window 130and the display panel 110. Then, the sensor pixels PXLi may outputsensing signals corresponding to incident light. The sensing signalsoutput from the sensor pixels PXLi may be input to the sensor driver220, and the sensor driver 220 may generate fingerprint information ofthe user by aggregating respective output signals of the sensor pixelsPXLi. In one embodiment, for example, reflected light components thathave been reflected from respective ridges and valleys of thefingerprint and are incident on the sensor pixels PXLi may havedifferent quantities of light or different waveforms. Therefore, theform (pattern) of the fingerprint may be detected by aggregating thesensing signals received from the sensor pixels PXLi and by identifyingthe ridges and valleys of the fingerprint. In such an embodiment,various types of information as well as the user's fingerprint may beobtained through a light-sensing (photodetection) scheme using the imagesensor 120.

In an embodiment, as shown in FIGS. 5A and 5B, a fingerprint or the likemay be sensed using the internal light of the display panel 110 emittedfrom at least some display pixels PXLd, but the disclosure is notlimited thereto. In an alternative embodiment, a separate light sourcemay be arranged inside and/or outside the display device 10 and isdriven during a sensing period in which the image sensor 120 isactivated, thus enabling a fingerprint or the like to be sensed.

FIG. 6 is a circuit diagram illustrating a display pixel PXLd accordingto an embodiment of the disclosure. Particularly, FIG. 6 shows a displaypixel PXLd arranged in the display area DA of FIGS. 2 and 3 . In FIG. 6, a display pixel PXLd arranged in an i-th row (where i is a naturalnumber) and a j-th column (where j is a natural number) of the displayarea DA is illustrated. In an embodiment, display pixels PXLd arrangedin the display area DA of FIGS. 2 and 3 may have substantially a samestructure as that shown in FIG. 6 . In one embodiment, for example, thedisplay pixels PXLd may be formed or disposed in the display area DA ina repeating pattern while having substantially the same structure in abackplane layer in which respective pixel circuits PXC are arranged andin a light-emitting element layer in which respective light-emittingelements EL are arranged. However, the disclosure is not limitedthereto. In an alternative embodiment, at least one display pixel PXLdmay have a structure different from that of the remaining display pixelsPXLd.

Referring to FIG. 6 , an embodiment of the display pixel PXLd mayinclude a light-emitting element EL coupled (e.g., electricallyconnected) between a first pixel power source ELVDD and a second pixelpower source ELVSS, and a pixel circuit PXC coupled between the firstpixel power source ELVDD and the light-emitting element EL and furthercoupled to a corresponding scan line SLi and a corresponding data lineDLj and configured to control a driving current flowing through thelight-emitting element EL. However, the location of the pixel circuitPXC is not limited thereto. In one embodiment, for example, the pixelcircuit PXC may also be coupled between the light-emitting element ELand the second pixel power source ELVSS. In an embodiment, where thedisplay pixel PXLd is a passive pixel, the pixel circuit PXC may beomitted. In such an embodiment, both ends (e.g., an anode electrode anda cathode electrode) of the light-emitting element EL may be directlycoupled to a predetermined power line (e.g., a first or second powerline) and a predetermined signal line (e.g., a scan line SLi or a dataline DLj).

The first pixel power source ELVDD and the second pixel power sourceELVSS may have different potentials or voltages from each other. In oneembodiment, for example, the first pixel power source ELVDD may be setto high-potential power, and the second pixel power source ELVSS may beset to low-potential power. A potential difference between the firstpixel power source ELVDD and the second pixel power source ELVSS, thatis, a voltage applied therebetween, may be greater than the thresholdvoltage of the light-emitting element EL.

The light-emitting element EL may be coupled to the first pixel powersource ELVDD via the pixel circuit PXC. In one embodiment, for example,an anode electrode of the light-emitting element EL may be coupled tothe first pixel power source ELVDD via a second transistor T2. In suchan embodiment, a cathode electrode of the light-emitting element EL maybe coupled to the second pixel power source ELVSS. In such anembodiment, the light-emitting element EL emits light with luminancecorresponding to the driving current supplied from the pixel circuitPXC. In an embodiment, the light-emitting element EL may be, but is notlimited to, an organic light-emitting diode (“OLED”) including anorganic light-emitting layer. In an alternative embodiment, micro-sizedinorganic light-emitting elements, the sizes of which are nanoscale ormicroscale levels, may constitute the light source of the display pixelPXLd.

The pixel circuit PXC may include first and second transistors T1 and T2and a capacitor C. The first transistor (hereinafter also referred to as“switching transistor”) T1 may be coupled between the data line DLj anda first node N1. In such an embodiment, a gate electrode of the firsttransistor T1 may be coupled to a scan line SLi. The first transistor T1may be turned on when a scan signal having a gate-on voltage (e.g., alow voltage) is supplied through the scan line SLi, thus electricallycoupling the data line DLj to the first node N1. In such an embodiment,when the first transistor T1 is turned on, a data signal suppliedthrough the data line DLj may be transferred to the first node N1.

The second transistor (hereinafter also referred to as “drivingtransistor”) T2 may be coupled between the first pixel power sourceELVDD and the light-emitting element EL. In such an embodiment, a gateelectrode of the second transistor T2 may be coupled to the first nodeN1. The second transistor T2 controls the driving current flowing intothe light-emitting element EL in response to the voltage of the firstnode N1. In one embodiment, for example, the second transistor T2 maycontrol the supply/non-supply of the driving current and/or themagnitude of the driving current in response to the voltage of the firstnode N1.

The capacitor C may be coupled between the first pixel power sourceELVDD and the first node N1. In such an embodiment, the capacitor Cstores a voltage corresponding to a data signal supplied to the firstnode N1 during each frame period.

In embodiments of the invention, the type and structure of the displaypixel PXLd are not limited to those illustrated in FIG. 6 . In anembodiment, the display pixel PXLd may be configured as any of pixelsthat conform to currently known various types, structures and/or drivingschemes. Further, in FIG. 6 , although an embodiment of the displaypixel PXLd where the display device 10 is a light-emitting displaydevice (e.g., an organic light-emitting display device), is illustrated,the disclosure is not limited thereto. In an embodiment, the structure,the driving scheme, etc. of the display pixel PXLd may be variouslymodified or changed in various manners depending on the type, structureand/or driving scheme of the display device 10.

FIG. 7 is a sectional view illustrating a display pixel PXLd accordingto an embodiment of the disclosure. Particularly, FIG. 7 illustrates asection of an embodiment of the display pixel PXLd illustrated in FIG. 6. For convenience of description, only a portion of the display pixelPXLd (e.g., a region in which the light-emitting element EL and thesecond transistor T2 coupled thereto are arranged) is illustrated inFIG. 7 . In an embodiment, the first transistor T1 of the display pixelPXLd may have a sectional structure substantially identical or similarto that of the second transistor T2, but the transistor structure of thedisclosure is not limited thereto. In an embodiment, at least one ofelectrodes forming the capacitor C may be arranged in a same layer as atleast one of the electrodes constituting the first and secondtransistors T1 and T2, but the disclosure is not limited thereto.

Referring to FIGS. 6 and 7 , each display pixel PXLd may be disposed ona surface of a base layer BSL that is the basic material of the displaypanel 110. In one embodiment, for example, each display pixel PXLd maybe disposed in the corresponding pixel area PXA on the base layer BSL.

The base layer BSL may be a rigid or flexible substrate, and theproperty or material thereof is not particularly limited. In oneembodiment, for example, the base layer BSL may be manufactured as arigid substrate including or formed of a glass or a tempered glass, athin-film substrate having flexibility, or an insulating layer having asingle-layer structure or a multi-layer structure.

In an embodiment, a buffer layer BFL may be disposed on a surface of thebase layer BSL. The buffer layer BFL may effectively prevent impuritiesfrom being diffused from the base layer BSL and may improve the flatnessof the base layer BSL. The buffer layer BFL may have a single-layerstructure or a multi-layer structure including two or more layers. In anembodiment, the buffer layer BFL may be an inorganic insulating layerincluding or formed of an inorganic material. In one embodiment, forexample, the buffer layer BFL may include or be formed of siliconnitride, silicon oxide or silicon oxynitride, for example. In anembodiment, where the buffer layer BFL has a multi-layer structure,individual layers of the buffer layer BFL may include or be formed of asame material as each other or different materials from each other.Alternatively, the buffer layer BFL may be omitted.

In an embodiment, various types of circuit elements constituting thepixel circuit PXC, together with the second transistor T2, may bedisposed on the buffer layer BFL. In an embodiment, during a process forforming the circuit elements, wires (or lines) including various powerlines and/or signal lines may be formed together with the circuitelements. In one embodiment, for example, at processing steps at whichthe circuit elements of the pixel circuit PXC are formed, first andsecond power lines for supplying power from the first pixel power sourceELVDD and the second pixel power source ELVSS and the scan line SLi andthe data line DLj for transferring a scan signal and a data signal tothe corresponding display pixel PXLd may be formed together.

The second transistor T2 may include an active layer ACT, a gateelectrode GE, a source electrode SE, and a drain electrode DE. In anembodiment, the active layer ACT may be disposed on the buffer layer BFLand may include or be made of a semiconductor material. In oneembodiment, for example, the active layer ACT may be a semiconductorpattern including polysilicon, amorphous silicon, an oxidesemiconductor, or the like, and may be a semiconductor layer doped orundoped with impurities. Alternatively, only a region of the activelayer ACT may be selectively doped with impurities.

A gate insulating layer GI may be disposed on the active layer ACT, andthe gate electrode GE may be disposed on the gate insulating layer GI.In an embodiment, the scan line SLi may be formed together with the gateelectrode GE during a same process,.

An interlayer insulating layer IL may be disposed on the gate electrodeGE, and the source electrode SE and the drain electrode DE may bedisposed on the interlayer insulating layer IL. The source electrode SEand the drain electrode DE may be coupled to different regions of theactive layer ACT by respective contact holes CH defined through the gateinsulating layer GI and the interlayer insulating layer IL.

In an embodiment, as shown in FIG. 7 , the source electrode SE and thedrain electrode DE are disposed in a layer different from a layer inwhich the active layer ACT is disposed, but the disclosure is notlimited thereto. In an alternative embodiment, the source electrode SEand/or the drain electrode DE may extend from both ends of the activelayer ACT and may be integrated with the active layer ACT.

A passivation layer PSV (hereinafter also referred to as a“planarization layer”) may be disposed on the source electrode SE andthe drain electrode DE. The passivation layer PSV may substantiallyplanarize the top surface of the pixel circuit PXC while covering theentire surface of the pixel circuit PXC including the second transistorT2.

In accordance with an embodiment, the base layer BSL, the circuitelements (e.g., circuit elements constituting each pixel circuit PXCincluding the second transistor T2) disposed on a surface of the baselayer BSL and various types of power lines and/or wires formed togetherwith the circuit elements may define the backplane layer BPL of thedisplay device 10. In one embodiment, for example, the backplane layerBPL may include the base layer BSL and a circuit element layer (e.g., acircuit element layer in which the pixel circuit PXC and/or varioustypes of lines are disposed) disposed on a surface of the base layerBSL. The light-emitting element EL may be disposed on the passivationlayer PSV.

Each light-emitting element EL may include a first pixel electrode PXE1,a light-emitting layer EML, and a second pixel electrode PXE2 which aresequentially disposed in a light-emitting area EMA of the correspondingdisplay pixel PXLd.

The first pixel electrode PXE1 may be disposed on the passivation layerPSV and may be coupled to one electrode of the second transistor T2, forexample, the drain electrode DE, through a via hole VH defined throughthe passivation layer PSV. In an embodiment, the first pixel electrodePXE1 may be, but is not limited to, an anode electrode of thelight-emitting element EL.

A pixel-defining layer PDL which defines each pixel area PXA (especiallythe light-emitting area EMA) may be disposed on a surface of the baselayer BSL on which the first pixel electrode PXE1 or the like isdisposed. The pixel-defining layer PDL may be disposed between thelight-emitting areas EMA of respective display pixels PXLd and anopening for exposing the first pixel electrode PXE1 from thecorresponding light-emitting area EMA is defined in the pixel-defininglayer PDL. In one embodiment, for example, the pixel-defining layer PDLmay upwardly protrude from the surface of the base layer BSL, on whichthe first pixel electrode PXE1 or the like is disposed, along theperiphery of each light-emitting area EMA.

The light-emitting layer EML may be disposed in each light-emitting areasurrounded by the pixel-defining layer PDL. The light-emitting layer EMLmay be disposed on the exposed surface of the first pixel electrodePXE1. In an embodiment, the light-emitting layer EML may have amulti-layer thin-film structure including at least a light generationlayer LGL. In one embodiment, for example, the light-emitting layer EMLmay include the light generation layer LGL for emitting light in apredetermined color, a first common layer HCL interposed between thelight generation layer LGL and the first pixel electrode PXE1, and asecond common layer ECL interposed between the light generation layerLGL and the second pixel electrode PXE2. In an embodiment, the firstcommon layer HCL may include at least one of a hole injection layer anda hole transport layer. In an embodiment, the second common layer ECLmay include at least one of a hole blocking layer, an electron transportlayer, and an electron injection layer. In an embodiment, the lightgeneration layer LGL may be individually patterned in accordance withthe corresponding light-emitting area EMA. In an embodiment, the firstcommon layer HCL and the second common layer ECL may be disposed tocover an entire surface of the display area DA.

In an embodiment, the second pixel electrode PXE2 may be disposed on thelight-emitting layer EML. In an embodiment, the second pixel electrodePXE2 may be, but is not limited to, a cathode electrode of thelight-emitting element EL. In an embodiment, the second pixel electrodePXE2 may be disposed to cover an entire surface of the display area DA,but the disclosure is not limited thereto.

In an embodiment, the first pixel electrodes PXE1 disposed in respectivepixel areas PXA, the light-emitting layer EML disposed on the firstpixel electrodes PXE1, and the second pixel electrode PXE2 disposed onthe light-emitting layer EML may constitute or collectively define alight-emitting element layer ELL of the display device 10. In oneembodiment, for example, the light-emitting element layer ELL mayinclude a first pixel electrode layer including the first pixelelectrodes PXE1 of the display pixels PXLd, light-emitting layers EMLdisposed on the first pixel electrodes PXE1, and a second pixelelectrode layer including the second pixel electrode PXE2 disposed onthe light-emitting layers EML.

A thin-film encapsulation layer TFE configured to encapsulate the secondpixel electrode PXE2 may be disposed on the second pixel electrode PXE2.The thin-film encapsulation layer TFE may be disposed in a portion(e.g., at least the display area DA) of the display panel 110, in whichthe display pixels PXLd are disposed, and may encapsulate the displaypixels PXLd. In an embodiment including the thin-film encapsulationlayer TFE, the thickness of the display panel 110 may be reduced, andthe flexibility of the display panel 110 may be secured while thedisplay pixels PXLd are effectively protected.

In an embodiment, the thin-film encapsulation layer TFE may have amulti-layer structure or a single-layer structure. In one embodiment,for example, the thin-film encapsulation layer TFE may have amulti-layer structure including at least two overlapping inorganiclayers and at least one organic layer interposed between the inorganiclayers. Alternatively, the thin-film encapsulation layer TFE may have asingle organic/inorganic hybrid insulating layer. In accordance with anembodiment, the thin-film encapsulation layer TFE may be replaced withan encapsulation substrate ENC including or made of a glass or a plasticmaterial. In one embodiment, for example, the encapsulation substrateENC may be disposed in the display area DA in a way such that at leastthe display pixels PXLd may be encapsulated. In accordance with anembodiment, the thin-film encapsulation layer TFE or the encapsulationsubstrate ENC for encapsulating the display pixels PXLd may form anencapsulation layer ENL of the display device 10.

In an embodiment, the backplane layer BPL, which includes the base layerBSL and selectively includes the circuit element layer (i.e., thecircuit layer in which circuit elements constituting each pixel circuitPXC and various types of lines coupled to the circuit elements aredisposed), the light-emitting element layer ELL, which includeslight-emitting elements EL disposed in each pixel area PXA on thebackplane layer BPL, and the encapsulation layer ENL, which is disposedon the display pixels PXLd including the light-emitting elements EL, mayconstitute the display panel 110. Accordingly, the display panel 110 maygenerate light corresponding to a data signal.

FIG. 8 is a circuit diagram illustrating a sensor pixel PXLi accordingto an embodiment of the disclosure. Particularly, FIG. 8 shows a sensorpixel PXLi arranged in the sensing area SA of FIGS. 2 and 3 . In anembodiment, sensor pixels PXLi arranged in the sensing area SA of FIGS.2 and 3 may have substantially the same structure as each other, but thedisclose is not limited thereto.

Referring to FIG. 8 , an embodiment of the sensor pixel PXLi may includea light-sensing element PD. The light-sensing element PD may be anelement for generating an electrical signal corresponding to a lightreceiving amount, and may be, for example, a photodiode. In accordancewith an embodiment, the photodiode may be, but is not limited to, one ofvarious types of photodiodes, such as a PIN diode and an avalanche photodetector (“APD”) diode.

In an embodiment, the sensor pixel PXLi may further include a storagecapacitor Cst which stores photocharges generated by the light-sensingelement PD, a first transistor M1 which transfers a reset voltage to afirst node N1 coupled to the storage capacitor Cst, and an amplifier AMPwhich includes a plurality of transistors for generating and amplifyinga sending signal corresponding to the voltage of the first node N1.

The first transistor M1 may be coupled between a first power source VDDand the first node N1, and a gate electrode of the first transistor M1may be coupled to a first control line CTL1. The first transistor M1 isturned on when a first control signal having a gate-on voltage (e.g., ahigh voltage) is supplied from the first control line CTL1, and thentransfers the voltage of the first power source VDD to the first nodeN1. In an embodiment, the first power source VDD may be a high-potentialoperating power source of the image sensor 120.

The light-sensing element PD may be coupled between the first node N1and a second power source VSS. In one embodiment, for example, thelight-sensing element PD may be implemented as a photodiode coupled in areverse direction between the first node N1 and the second power sourceVSS. The light-sensing element PD includes a light-receiving unit onwhich light can be incident and generates photocharges in response tothe incident light. In an embodiment, the second power source VSS may bea low-potential or reference potential operating power source of theimage sensor 120. In one embodiment, for example, the second powersource VSS may have, but is not limited to, a ground level.

The storage capacitor Cst may be coupled in parallel to thelight-sensing element PD between the first node N1 and the second powersource VSS. The storage capacitor Cst stores the photocharges generatedby the light-sensing element PD.

The amplifier AMP may include at least two transistors coupled in seriesbetween the first power source VDD and an output line OUT. The amplifierAMP outputs a sensing signal corresponding to the voltage of the firstnode N1 in response to a first driving signal supplied from a firstdriving line DRL1. The output line OUT may be a line, through which thesensing signal generated from each sensor pixel PXLi is output, and maybe coupled to each RX channel configured in the sensor driver 220.

In an embodiment, the amplifier AMP may be a two-stage cascode amplifierincluding or defined by a second transistor M2 and a third transistor M3coupled in series between the first power source VDD and the output lineOUT. In an embodiment, each of the second and third transistors M2 andM3 may be, but is not limited to, a field-effect transistor.

The second transistor M2 may be coupled between the first power sourceVDD and the output line OUT, and a gate electrode of the secondtransistor M2 may be coupled to the first node N1. In such anembodiment, the second transistor M2 generates an electrical signal(hereinafter referred to as a “sensing signal”) having a magnitudecorresponding to the voltage of the first node N1.

The third transistor M3 may be coupled between the second transistor M2and the output line OUT, and a gate electrode of the third transistor M3may be coupled to the first driving line DRL1. The third transistor M3is turned on when the first driving signal having a gate-on voltage issupplied from the first driving line DRL1, and then amplifies andoutputs the sensing signal transferred from the second transistor M2.

FIG. 9 is a signal timing diagram illustrating an embodiment of inputsignals for driving the sensor pixel PXLi of FIG. 8 . For convenience ofdescription, input signals that are supplied to the sensor pixel PXLiduring one cycle (1P) of a sensing period in which the sensor pixel PXLiis activated are illustrated in FIG. 9 , and the input signals may berepeatedly supplied to the sensor pixel PXLi during every cycle of thesensing period.

Referring to FIGS. 8 and 9 , during each cycle (1P) of the sensingperiod in which the sensor pixel PXLi is activated, a first controlsignal Vrst and the first driving signal Vdr1, each having a gate-onvoltage, may be sequentially supplied to the sensor pixel PXLi throughthe first control line CTL1 and the first driving line DRL1,respectively. In one embodiment, for example, the first control signalVrst and the first driving signal Vdr1, each having a gate-on voltage,may be sequentially supplied to the sensor pixel PXLi at an interval ofa predetermined time (i.e., with a time difference) during each cycle(1P).

In such an embodiment, as shown in FIG. 9 , during a first interval t1,the first control signal Vrst having a gate-on voltage may be suppliedthrough the first control line CTL1. Then, the first transistor M1 isturned on in response to the first control signal Vrst.

When the first transistor M1 is turned on, the voltage of the firstpower source VDD is transferred to the first node N1 while the voltageof the first node N1 is reset to the voltage of the first power sourceVDD. Accordingly, charges accumulated in the storage capacitor Cstduring a previous cycle are reset.

Thereafter, the supply of the first control signal Vrst having a gate-onvoltage is stopped, and the voltage of the first control line CTL1 ischanged to a gate-off voltage. Accordingly, as the first transistor M1is turned off, the first power source VDD is disconnected from the firstnode N1.

When light is incident on each light-sensing element PD during the firstinterval t1, the light-sensing element PD may generate photochargescorresponding to the incident light, and the generated photocharges arestored in the capacitor Cst. Accordingly, a voltage corresponding to theincident light is applied to the first node N1.

Thereafter, during a second interval t2, when the first driving signalVdr1 (hereinafter also referred to as a “Tx signal”, “readout signal” or“selection signal”) having a gate-on voltage is supplied through thefirst driving line DRL1, the third transistor M3 is turned on. Then, asensing signal generated in the second transistor T2 in response to thevoltage of the first node N1 is output through the output line OUT viathe third transistor M3. In such an embodiment, the second transistor M2is turned on to a degree corresponding to the voltage of the first nodeN1, and then a sensing signal having a magnitude corresponding to thevoltage of the first node N1 is generated. In such an embodiment, thethird transistor M3 amplifies and outputs the sensing signal to a levelcorresponding to a gain value. The sensing signal output through eachoutput line OUT may be input to the corresponding Rx channel of thesensor driver 220, and may be used to generate sensed information, suchas a fingerprint.

In accordance with an embodiment of the sensor pixel PXLi and the imagesensor 120 including the sensor pixel PXLi, as shown in FIGS. 8 and 9 ,charges accumulated in the storage capacitor Cst may be converted into avoltage signal depending on the light-receiving amount of each sensorpixel PXLi, and the voltage signal may be output. In such an embodiment,the sensing signal may be amplified within the sensor pixel PXLidepending on the gain of the amplifier AMP in each sensor pixel PXLi,and the amplified sensing signal is output. Accordingly, the influenceof noise may be reduced, and signal-to-noise ratio (“SNR”) may beeffectively improved. Therefore, in accordance with embodiments of theinvention, when the image sensor 120 is implemented as a high-resolutionimage senor and/or as a large-sized image sensor, high sensitivityfeatures may be secured.

In a case where the image sensor 120 is implemented as a high-resolutionimage sensor and/or a large-sized image sensor, the sizes of thelight-sensing element PD and the storage capacitor Cst of each sensorpixel PXLi may be reduced, such that the distance between the sensorpixel PXLi and the RX channel coupled thereto is increased, thusincreasing the capacitance of a parasitic capacitor. Accordingly, SNR ofeach sensing signal may be decreased, and thus the image sensor isvulnerable to noise. In embodiments of the disclosure, SNR may beimproved when the sensing signal is amplified within each sensor pixelPXLi and is then output while photocharges corresponding to incidentlight are converted into a voltage-type sensing signal and thevoltage-type sensing signal is output. Accordingly, the high-sensitivityimage sensor 120 and the display device 10 having the image sensor 120may be provided.

FIG. 10 is a circuit diagram illustrating a sensor pixel PXLi accordingto an embodiment of the disclosure. In the embodiment of FIG. 10 , thesame reference numerals are used to designate components similar oridentical to those in the embodiment of FIG. 8 , and any repetitivedetailed description thereof will be omitted.

Referring to FIG. 10 , an embodiment of a sensor pixel PXLi may furtherinclude a transfer transistor Md (hereinafter also referred to as a“sixth transistor”). In such an embodiment, an image sensor 120including the sensor pixel PXLi may further include a second controlline CTL2 coupled to the transfer transistor Md of the sensor pixelPXLi.

The transfer transistor Md may be coupled between a first node N1 and alight-sensing element PD, and a gate electrode of the transfertransistor Md may be coupled to the second control line CTL2. In such anembodiment, the transfer transistor Md is turned on when a secondcontrol signal having a gate-on voltage is supplied from the secondcontrol line CTL2. When the transfer transistor Md is turned on,photocharges accumulated in the light-sensing element PD are transferredto the first node N1.

FIG. 11 is a signal timing diagram illustrating embodiments of inputsignals for driving the sensor pixel PXLi of FIG. 10 . In the embodimentof FIGS. 10 and 11 , any repetitive detailed description of componentssimilar or identical to those of the embodiment of FIGS. 8 and 9 will beomitted.

Referring to FIGS. 10 and 11 , during each cycle (1P) of a sensingperiod in which the sensor pixel PXLi is activated, a first controlsignal Vrst and a second control signal Vdlv, each having a gate-onvoltage, may be sequentially supplied to the sensor pixel PXLi through afirst control line CTL1 and the second control line CTL2, respectively.In one embodiment, for example, the first control signal Vrst and thesecond control signal Vdlv, each having a gate-on voltage, may besequentially supplied to the sensor pixel PXLi at an interval of apredetermined time (i.e., with a time difference) during each cycle(1P). In an embodiment, a first driving signal Vdr1 having a gate-onvoltage may be individually supplied subsequent to the first and secondcontrol signals Vrst and Vdlv a plurality of times during each cycle(1P) of the sensing period. In one embodiment, for example, during eachcycle 1P of the sensing period, the first control signal Vrst, a primaryfirst driving signal Vdr1, the second control signal Vdlv, and asecondary first driving signal Vdr1 may be sequentially supplied.

In such an embodiment, during a first interval t1, when the firstcontrol signal Vrst having a gate-on voltage is supplied through thefirst control line CTL1, the first transistor M1 is turned on.Accordingly, as the voltage of the first power source VDD is transferredto the first node N1, the voltage of the first node N1 is reset.

Thereafter, during a second interval t2, when the primary first drivingsignal Vdr1 having a gate-on voltage is supplied, the third transistorM3 is turned on. Accordingly, a first sensing signal (hereinafter alsoreferred to as an “initial sensing signal”) corresponding to the voltageof the first node N1 is output through the output line OUT.

Thereafter, during a third interval t3, when the second control signalVdlv having a gate-on voltage is supplied through the second controlline CTL2, the transfer transistor Md is turned on. Accordingly,photocharges generated by the light-sensing element PD are transferredto the first node N1.

Thereafter, during a fourth interval t4, when the secondary firstdriving signal Vdr1 having a gate-on voltage is supplied, the thirdtransistor M3 is turned on. Accordingly, a second sensing signal(hereinafter also referred to as a “light-sensing signal”) correspondingto the voltage of the first node N1 is output through the output lineOUT.

Then, the sensor driver 220 may detect the difference between the firstsensing signal and the second sensing signal that are sequentially inputthrough respective Rx channels and may detect a change between thesensing signals depending on the incident light based on the difference.

In an embodiment, as shown in FIGS. 10 and 11 , the sensor pixel PXLiand the image sensor 120 including the sensor pixel PXLi may convertcharges accumulated in the storage capacitor Cst into a voltage signaland output the voltage signal, and may amplify and output the sensingsignal generated within the sensor pixel PXLi. Accordingly, theinfluence of noise may be reduced, and SNR may be effectively improved.

In such an embodiment, the sensor pixel PXLi and the image sensor 120including the sensor pixel PXLi may output the voltage of the first nodeN1 that has been generated depending on a reset and the voltage of thefirst node N1 that has changed depending on the transfer of photochargesaccumulated in the light-sensing element PD due to incident light in atime division manner. Then, the sensor driver 220 may detect the changebetween sensing signals depending on incident light based on thedifferences between the first and second sensing signals that are outputfrom respective sensor pixels PXLi. Accordingly, sensing signalsdepending on the quantities of light incident on respective sensorpixels PXLi may be more accurately detected.

FIG. 12 is a circuit diagram illustrating a sensor pixel PXLi accordingto another alternative embodiment of the disclosure. In the embodimentof FIG. 12 , the same reference numerals are used to designatecomponents similar or identical to those in the above-describedembodiments (e.g., the embodiment of FIG. 10 ), and a detaileddescription of the components will be omitted.

Referring to FIG. 12 , an embodiment of a sensor pixel PXLi may includea multistage amplifier AMP including three or more transistors coupledin series between a first power source VDD and an output line OUT. Inone embodiment, for example, the amplifier AMP may be implemented as athree-stage cascode amplifier.

In an embodiment, the amplifier AMP may include a second transistor M2which generates a sensing signal corresponding to the voltage of a firstnode N1 and a third transistor M3 and a fourth transistor M4 whichamplify and output sensing signals transferred from the secondtransistor M2 (e.g., first and second sensing signals). In oneembodiment, for example, the third and fourth transistors M3 and M4 mayamplify and output the sensing signals transferred from the secondtransistor M2 during an interval in which a first driving signal Vdr1having a gate-on voltage is supplied from a first driving line DRL1.

In accordance with an embodiment, gate electrodes of the third andfourth transistors M3 and M4 may be coupled in common to the firstdriving line DRL1. Accordingly, the first driving signal Vdr1 suppliedfrom the first driving line DRL1 may be transferred both to the thirdand fourth transistors M3 and M4.

In such an embodiment, the magnitudes (e.g., voltages) of the firstdriving signal Vdr1 transferred to the gate electrodes of the third andfourth transistors M3 and M4 may be different from each other. In oneembodiment, for example, each sensor pixel PXLi may further include afirst resistor element R1 coupled between the gate electrode of thethird transistor M3 and the first driving line DRL1. Accordingly, thefirst driving signal Vdr1 transferred to the gate electrode of the thirdtransistor M3 may have a magnitude lower than that of the first drivingsignal Vdr1 transferred to the gate electrode of the fourth transistorM4.

The third and fourth transistors M3 and M4 may sequentially amplify andoutput the sensing signal transferred from the second transistor M2during an interval in which the first driving signal Vdr1 having agate-on voltage is supplied from the first driving line DRL1. In anembodiment, the sensing signal from the second transistor M2 may beamplified twice while sequentially passing through the third and fourthtransistors M3 and M4. Accordingly, In such an embodiment, the sensingsignal may be more effectively amplified. Therefore, in accordance withthe above-described embodiment, SNR of the sensing signal output fromeach sensor pixel PXLi may be more effectively improved, and thesensitivity of the image sensor 120 may be improved.

In an embodiment of FIG. 12 , the sensor pixel PXLi may include thetransfer transistor Md, similarly to the embodiment of FIG. 10 , but thetransfer transistor Md may be selectively omitted. In the embodiment ofFIG. 12 and other embodiments which will be described later, the sensorpixel PXLi may or may not include the transfer transistor MD.

FIG. 13 is a circuit diagram illustrating a sensor pixel PXLi accordingto another alternative embodiment of the disclosure. In the embodimentof FIG. 13 , the same reference numerals are used to designatecomponents similar or identical to those in the above-describedembodiments (e.g., the embodiment of FIG. 12 ), and any repetitivedetailed description of thereof will be omitted.

Referring to FIG. 13 , a first resistor element R1′ may include atransistor element Mr coupled in the form of a diode between a firstdriving line DRL1 and a gate electrode of a third transistor M3. In oneembodiment, for example, the first resistor element R1′ may beimplemented as the transistor element Mr alone or may further include anadditional resistor element in addition to the transistor element Mr.

The transistor element Mr may decrease the voltage of a first drivingsignal Vdr1 supplied from the first driving line DRL1 by a thresholdvoltage, and may transfer the decreased voltage to the gate electrode ofthe third transistor M3. Accordingly, as described above with referenceto FIG. 12 , a sensing signal generated from the second transistor M2may be amplified twice while sequentially passing through the third andfourth transistors M3 and M4 during an interval in which the firstdriving signal Vdr1 having a gate-on voltage is supplied from the firstdriving line DRL1.

FIG. 14 is a circuit diagram illustrating a sensor pixel PXLi accordingto another alternative embodiment of the disclosure. FIG. 15 is a signaltiming diagram illustrating an embodiment of input signals for drivingthe sensor pixel PXLi of FIG. 14 . In the embodiments of FIGS. 14 and 15, the same reference numerals are used to designate components similaror identical to those in the above-described embodiments, and thus anyrepetitive detailed description thereof will be omitted.

Referring to FIGS. 14 and 15 , in an embodiment of the sensor pixelPXLi, a third transistor M3 and a fourth transistor M4 may be coupled todifferent driving lines, respectively. In one embodiment, for example, agate electrode of the fourth transistor M4 may be coupled to a firstdriving line DRL1 through which a first driving signal Vdr1 is supplied,and a gate electrode of the third transistor M3 may be coupled to asecond driving line DRL2 through which a second driving signal Vdr2 issupplied. In such an embodiment, the image sensor 120 may be coupled toeach sensor pixel PXLi, and may include first and second driving linesDLR1 and DRL2 that are separate or disconnected from each other.

In an embodiment, the first and second driving signals Vdr1 and Vdr2 maybe supplied to temporally overlap each other. Here, the supply of thefirst and second driving signals Vdr1 and Vdr2 to temporally overlapeach other may mean that times during which the first and second drivingsignals Vdr1 and Vdr2 are supplied overlap each other. In oneembodiment, for example, the first and second driving signals Vdr1 andVdr2 may be simultaneously supplied. However, the disclosure is notlimited thereto. In an alternative embodiment, the first and seconddriving signals Vdr1 and Vdr2 may be supplied to merely partiallyoverlap each other.

In an embodiment, the first and second driving signals Vdr1 and Vdr2 mayhave different magnitudes from each other. In one embodiment, forexample, the second driving signal Vdr2 may have a gate-on voltage(e.g., a gate-on voltage lower than that of the first driving signalVdr1). Accordingly, during the intervals in which first and seconddriving signals Vdr1 and Vdr2, each having a gate-on voltage, aresupplied from the first and second driving lines DRL1 and DRL2, thesensing signal generated from the second transistor M2 may be amplifiedtwice, and the amplified signal may be output.

FIG. 16 is a circuit diagram illustrating a sensor pixel PXLi accordingto another alternative embodiment of the disclosure. In the embodimentof FIG. 16 , the same reference numerals are used to designatecomponents similar or identical to those in the above-describedembodiments (e.g., the embodiment of FIG. 12 ), and any repetitivedetailed description thereof will be omitted.

Referring to FIG. 16 , an amplifier AMP may be implemented as afour-stage cascode amplifier which further includes a fifth transistorM5 and a second resistor element R2, in addition to the elements of theamplifier described above with reference to FIG. 12 . In one embodiment,for example, the amplifier AMP may further include the fifth transistorM5 coupled between a third transistor M3 and a fourth transistor M4 andthe second resistor element R2 coupled to a gate electrode of the fifthtransistor M5. Alternatively, the amplifier AMP may also be implementedas a five or more-stage cascode amplifier by adding at least onetransistor and at least one resistor element.

The fifth transistor M5 may be coupled between the third transistor M3and the fourth transistor M4. The gate electrode of the fifth transistorM5 may be coupled between a first resistor element R1 and the secondresistor element R2.

The second resistor element R2 may be coupled between the first resistorelement R1 and the first driving line DRL1. Accordingly, the thirdtransistor M3, the fifth transistor M5, and the fourth transistor M4 maybe supplied with a gate-on voltage (i.e., a first driving signal Vdr1),the magnitude of which is gradually increased in the sequence of M3, M5,and M4.

In such an embodiment, a sensing signal from the second transistor M2may be amplified three times while sequentially passing through thethird transistor M3, the fifth transistor M5, and the fourth transistorM4. Accordingly, the sensing signal may be more effectively amplified,and thus SNR may be improved.

FIG. 17 is a circuit diagram illustrating a sensor pixel PXLi accordingto another alternative embodiment of the disclosure. FIG. 18 is a signaltiming diagram illustrating an embodiment of input signals for drivingthe sensor pixel PXLi of FIG. 17 . In the embodiments of FIGS. 17 and 18, the same reference numerals are used to designate components similaror identical to those in the above-described embodiments, and thus anyrepetitive detailed description thereof will be omitted.

Referring to FIGS. 17 and 18 , in an embodiment of the sensor pixelPXLi, the third to fifth transistors M3, M4, and M5 may be coupled todifferent driving lines from each other. In one embodiment, for example,a gate electrode of the third transistor M3 may be coupled to the seconddriving line DRL2 through which the second driving signal Vdr2 issupplied, and a gate electrode of the fifth transistor M5 may be coupledto a third driving line DRL3 through which the third driving signal Vdr3having a gate-on voltage higher than that of the second driving signalVdr2 is supplied. A gate electrode of the fourth transistor M4 may becoupled to a first driving line DRL1 through which a first drivingsignal Vdr1 having a gate-on voltage higher than those of the second andthird driving signals Vdr2 and Vdr3 is supplied. In this case, the imagesensor 120 may be coupled to each sensor pixel PXLi, and may includefirst, second, and third driving lines DRL1, DRL2, and DRL3 that areseparate from each other. Alternatively, the amplifier AMP may beimplemented as a five or more-stage cascode amplifier by adding at leastone transistor and forming a plurality of driving lines for separatelycontrolling individual transistors.

In an embodiment, the first, second, and third driving signals Vdr1,Vdr2, and Vdr3 may be supplied in a way such that times, during whichthe driving signals are supplied, temporally overlap each other. In oneembodiment, for example, the first, second, and third driving signalsVdr1, Vdr2, and Vdr3 may be simultaneously supplied. However, theconfiguration of the disclosure is not limited thereto. In analternative embodiment, the first, second, and third driving signalsVdr1, Vdr2, and Vdr3 may be supplied such that they only partiallyoverlap each other.

In one embodiment, for example, the first, second, and third drivingsignals Vdr1, Vdr2, and Vdr3 may have different magnitudes from eachother. In one embodiment, for example, the third driving signal Vdr3 mayhave a gate-on voltage having a magnitude greater than that of thesecond driving signal Vdr2 (e.g., a gate-on voltage higher than that ofthe second driving signal Vdr2) and may have a gate-on voltage having amagnitude less than that of the first driving signal Vdr1 (e.g., agate-on voltage lower than that of the first driving signal Vdr1).Accordingly, during intervals in which the first, second, and thirddriving signals Vdr1, Vdr2, and Vdr3 are supplied, the sensing signalgenerated from the second transistor M2 may be effectively amplified andoutput.

Alternative, the embodiments of FIGS. 16 and 17 may be applied incombination in such a way that two of the third to fifth transistors M3,M4, and M5 are coupled to the same driving line and in such a way thatat least one resistor element is coupled between the gate electrodes ofthe two transistors and the remaining transistor is coupled to a drivingline different from that of the two transistors. In such embodiments,sensor pixels PXLi may operate with reduced noise and improvedsensitivity. The embodiments set forth herein may be applied alone or,alternatively, at least two of the embodiments may be applied incombination.

In accordance with embodiments of the disclosure, each of the sensorpixels PXLi constituting the image sensor 120 may convert chargesaccumulated in response to incident light into the form of a voltagesignal and then output a sensing signal. In such embodiments, each ofthe sensor pixels PXLi may amplify the sensing signal using theamplifier AMP provided therein and may output the amplified sensingsignal through the corresponding output line OUT. Accordingly, theinfluence of noise may be reduced, and SNR may be effectively improved.In an embodiment, where a sensor pixel PXLi including a multistageamplifier AMP, such as a three or more-stage cascode structure, sensingsignals may be more effectively amplified and output. Therefore, in acase where the image sensor 120 is implemented as a high-resolutionimage sensor and/or a large-sized image sensor, sufficient sensitivitymay be secured.

Further, in accordance with an embodiment, either before each sensingperiod or periodically, the first node N1 is in a fully-depletion state,after which photocharges accumulated in the light-sensing element PD maybe transferred to the first node N1. Furthermore, in accordance with anembodiment, a correlated double sampling (“CDS”) scheme may be appliedto the output end of the image sensor 120, and thus noise may beremoved. Accordingly, sensing signals depending on the quantities oflight incident on respective sensor pixels PXLi may be more preciselydetected.

Although all transistors constituting each sensor pixel PXLi areillustrated as being N-type transistors, the disclosure is not limitedthereto. In an alternative embodiment, at least one of transistorsconstituting each sensor pixel PXLi may be changed to a P-typetransistor. In such an embodiment, a control signal and/or a drivingsignal for controlling the P-type transistor may have a gate-on voltage(e.g., a low voltage) at a voltage level differently from theabove-described embodiments.

In accordance with embodiments of the image sensor and the displaydevice including the image sensor according to the disclosure, each ofthe sensor pixels constituting the image sensor includes an amplifierfor amplifying and outputting a sensing signal corresponding to incidentlight. Accordingly, the influence of noise may be reduced, and SNR maybe effectively improved. In accordance with embodiments of thedisclosure, when an image sensor is implemented as a high-resolutionimage senor or as a large-sized image sensor, a high sensitivity imagesensor may be provided.

The invention should not be construed as being limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe concept of the invention to those skilled in the art.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, it will be understood bythose of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit or scopeof the invention as defined by the following claims.

What is claimed is:
 1. An image sensor comprising: a sensor pixelincluding: a first transistor coupled between a first power source and afirst node, wherein the first transistor is turned on in response to afirst control signal; a light-sensing element coupled between the firstnode and a second power source, wherein the light-sensing elementgenerates photocharges in response to incident light; and an amplifierincluding a plurality of transistors coupled in series between the firstpower source and an output line, wherein the amplifier outputs a sensingsignal corresponding to a voltage of the first node in response to afirst driving signal.
 2. The image sensor according to claim 1, furthercomprising: a storage capacitor coupled in parallel to the light-sensingelement between the first node and the second power source.
 3. The imagesensor according to claim 1, wherein the amplifier comprises: a secondtransistor coupled between the first power source and the output line,wherein the second transistor includes a gate electrode coupled to thefirst node; and a third transistor coupled between the second transistorand the output line, wherein the third transistor includes a gateelectrode coupled to a first driving line, the first driving line beingconfigured to supply the first driving signal.
 4. The image sensoraccording to claim 3, wherein the amplifier further comprises a fourthtransistor coupled between the third transistor and the output line, andthe fourth transistor outputs the sensing signal during the interval inwhich the first driving signal is supplied.
 5. The image sensoraccording to claim 4, further comprising: a first driving line coupledin common to gate electrodes of the third and fourth transistors,wherein the first driving line transmits the first driving signaltherethrough; and a first resistor element coupled between the gateelectrode of the third transistor and the first driving line.
 6. Theimage sensor according to claim 5, wherein the first resistor elementcomprises a transistor element coupled in a form of a diode between thefirst driving line and the gate electrode of the third transistor. 7.The image sensor according to claim 5, wherein the amplifier comprises:a second resistor element coupled between the first resistor element andthe first driving line; and a fifth transistor coupled between the thirdtransistor and the fourth transistor, wherein the fifth transistorincludes a gate electrode coupled between the first and second resistorelements.
 8. The image sensor according to claim 1, wherein, during eachcycle of a sensing period in which the sensor pixel is activated, thefirst control signal and the first driving signal are sequentiallysupplied to the sensor pixel at an interval of a predetermined time. 9.The image sensor according to claim 1, wherein the light-sensing elementis a photodiode.
 10. The image sensor according to claim 1, wherein thesensor pixel further comprises a transfer transistor coupled between thefirst node and the light-sensing element, wherein the transfertransistor is turned on in response to a second control signal.
 11. Theimage sensor according to claim 10, wherein the first and second controlsignals are sequentially supplied to the sensor pixel during each cycleof a sensing period during which the sensor pixel is activated, and thefirst driving signal is individually supplied subsequent to the firstand second control signals a plurality of times during each cycle.
 12. Adisplay device comprising: a display panel including a display pixel;and an image sensor including a sensor pixel, wherein the sensor pixelcomprises: a first transistor coupled between a first power source and afirst node, wherein the first transistor is turned on in response to afirst control signal; a light-sensing element coupled between the firstnode and a second power source, wherein the light-sensing elementgenerates photocharges in response to incident light; and an amplifierincluding a plurality of transistors coupled in series between the firstpower source and an output line, wherein the amplifier outputs a sensingsignal corresponding to a voltage of the first node in response to afirst driving signal.
 13. The display devicd according to claim 12,further comprising: a storage capacitor coupled in parallel to thelight-sensing element between the first node and the second powersource.
 14. The display device according to claim 12, wherein theamplifier comprises: a second transistor coupled between the first powersource and the output line, wherein the second transistor includes agate electrode coupled to the first node; and a third transistor coupledbetween the second transistor and the output line, wherein the thirdincludes a gate electrode coupled to a first driving line, the firstdriving line being configured to supply the first driving signal. 15.The display device according to claim 14, wherein the amplifier furthercomprises a fourth transistor coupled between the third transistor andthe output line, and the fourth transistor outputs a sensing signalduring the interval in which the first driving signal is supplied. 16.The display device according to claim 12, wherein, during each cycle ofa sensing period in which the sensor pixel is activated, the firstcontrol signal and the first driving signal are sequentially supplied tothe sensor pixel at an interval of a predetermined time.
 17. The displaydevice according to claim 12, wherein the sensor pixel further comprisesa transfer transistor coupled between the first node and thelight-sensing element, wherein the transfer transistor is turned on inresponse to a second control signal.
 18. The display device according toclaim 12, wherein the image sensor is arranged on a rear surface of thedisplay panel, and the sensor pixel is arranged in a sensing area whichoverlaps a portion of a display area in which the display pixel isarranged.